Separation systems, elements, and methods for separation utilizing stacked membranes and spacers

ABSTRACT

An example separation system includes a stack of membrane plate assemblies. An example membrane plate assembly may include membranes bonded to opposite sides of a spacer plate. The spacer plate may include a first opening in fluid communication with a region between the membranes, and a second opening in fluid communication with a region between membrane plate assemblies. Adjacent membrane plate assemblies in the stack may have alternating orientations such that bonding areas for adjacent membranes in the stack may be staggered. Accordingly, two isolated flows may be provided which may be orthogonal from one another.

CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.14/137,903, filed Dec. 20, 2013, which claims the filing benefit of U.S.provisional application No. 61/745,300, filed Dec. 21, 2012. Theseapplications are incorporated by reference herein in their entirety andfor all purposes.

GOVERNMENT SPONSORSHIP

This invention was made with Government support under contract numberW911NF-09-C-0079 awarded by the Department of Defense. The Governmenthas certain rights in this invention.

TECHNICAL FIELD

Examples described herein relate to separation systems, elements, andmethods which may be used for forward osmosis (FO), pressure retardedosmosis (PRO), or generally any separation process.

BACKGROUND

Membranes may be used to perform osmosis, which generally occurs whentwo solutions of differing concentration are placed on opposite sides ofa permeable or semi-permeable membrane. The osmotic pressure differencebetween the two solutions drives the permeation of water across themembrane from the dilute solution to the concentrated solution, whilethe selective property of the membrane retains the solutes in theirrespective solution.

Plate and frame separation elements may generally include a plate andframe for enclosing a stack or array of membrane plate assemblies. Plateand frame separation elements may include a combination of a flat sheetmembrane, a draw channel spacer, a flat sheet membrane, and feed channelspacer.

SUMMARY

Examples of separation systems, membrane plate assemblies, spacerplates, and methods are described herein. An example separation systemmay include a plurality of membrane plate assemblies. Each of themembrane plate assemblies may include a spacer plate having a spacingregion. The spacer plate may at least partially define a first openingand a second opening. The spacer plate may include a first surfacehaving a first bonding area and an opposing second surface having asecond bonding area. The membrane plate assemblies may each include afirst membrane bonded to the first surface at the first bonding area.The membrane plate assemblies may each includes second membrane bondedto the second surface at the second bonding area The membrane plateassemblies may form a stack, with adjacent membrane plate assemblies inthe stack having alternating orientations. The first surface and thesecond surface may have a staggered position with respect to oneanother. The first opening of the spacer plate may be in fluidcommunication with a region between the first and second membranesdefining a first flow path. The separation system may further includesupport plates coupled to hold the membrane elements in a stack, whereinat least one of the support plates defines at least one fluid port.

In some examples, the spacing region may include a sheet comprisingprotrusions, cavities, textures, or combinations thereof on both sides,wherein the protrusions, cavities, textures, or combinations thereof arein contact with the first membrane and the second membrane, defining aflow path across the spacing region.

In some examples, the spacing region comprises an inner membraneassembly, wherein the inner membrane assembly comprises a third membraneon a first side of the spacer plate, a fourth membrane on a second sideof the spacer plate.

In some examples, the separation system may further include a spacersheet between at least two adjacent membrane surfaces.

In some examples, the separation system may further include a spacersheet bonded to the first surface at the first bonding area andpositioned on a side of the first membrane opposite the spacer plate,wherein the side of the spacer sheet opposite to the first membrane ofthe first membrane plate assembly is in contact with the side of thesecond membrane of a second membrane plate assembly opposite to thespacer plate of the second membrane plate assembly.

In some examples, the second opening is in fluid communication with aregion between adjacent membrane plate assemblies in the stack defininga second flow path.

In some examples, the second opening is in fluid communication with aregion between adjacent membrane plate assemblies in the stack and thethird and fourth membranes defining a second flow path, and wherein thefirst opening is in fluid communication with regions between the firstand third membranes and the second and fourth membranes.

In some examples, the first flow path is configured to facilitate flowof a fluid in a first direction in the regions between the first andthird membranes and the second and fourth membranes and the second flowpath is configured to facilitate flow of a fluid in a second directionin the region between the third and fourth membranes and betweenadjacent membrane plate assemblies in the stack defining a second flowpath wherein the first and second directions are orthogonal.

In some examples, the at least one fluid port is in communication withthe first opening of at least one membrane plate assembly and anotherfluid port is in communication with the second opening of at least onemembrane plate assembly.

In some examples, the first and second openings are located on differentedges of the spacer plate.

In some examples, the first flow path is configured to facilitate flowof a fluid in a first direction in the region between the first andsecond membranes and the second flow path is configured to facilitateflow of a fluid in a second direction in the regions between adjacentplate assemblies, wherein the first and second directions areorthogonal.

In some examples, the first opening of each spacer plate is configuredto define any of a parallel, a series, or a series of parallel flowpaths for the first fluid.

In some examples, the second opening of each spacer plate is configuredto define any of a parallel, a series, or a series of parallel flowpaths for the second fluid.

In some examples, the first opening of each spacer plate is coupled toone or more of the fluid ports of one or more support plates.

In some examples, the second opening of each spacer plate is coupled toone or more of the fluid ports of one or more support plates.

In some examples, the separation system is immersed in a first fluid,and each of the first openings are exposed to the first fluid.

In some examples, another fluid port is coupled to the second openingsand is configured to provide a second fluid.

In some examples, each of the spacer plates is formed from an injectionmolded plastic.

In some examples, any of the first membranes or the second membranes areforward osmosis membranes.

In some examples, any of the first membranes or the second membranescomprise cellulose acetate, a thin film composite, polyimide, aramid,poly(vinylidene fluoride), or polypropylene.

In some examples, the membrane plate assemblies further compriseinterconnects configured to define a parallel flow path or a series flowpath.

An example method includes transporting a first fluid in a firstdirection in regions between certain ones of a plurality of membranes.An example method may further include transporting a second fluid in asecond direction in other regions between other ones of the plurality ofmembranes. The first and second fluids may each comprise solutes, andthe concentration of a solute may be higher in the first fluid such thatthe concentration of a solute in the second fluid is increased at leastin part by fluid transport across the membranes. The first and seconddirections may be perpendicular directions.

In some examples, at least pairs of the certain ones of the plurality ofmembranes are bonded to respective spacer plates to form the regions andthe respective spacer plates are stacked such that the bonded regions ofthe certain ones of the plurality of membranes are staggered in relationto one another.

In some examples, the regions between certain ones of the plurality ofmembranes are configured to define any of a parallel, a series, or aseries of parallel flow paths of the first fluid.

In some examples, the regions between other ones of the plurality ofmembranes are configured to define any of a parallel, a series, or aseries of parallel flow paths of the second fluid.

In some examples, at least pairs of the plurality of membranes arebonded to respective spacer plates, and the spacer plates are formedfrom an injection molded plastic.

In some examples, the membranes comprise cellulose acetate, a thin filmcomposite, polyamide, aramid, poly(vinylidene fluoride), polypropylene,or combinations thereof.

In some examples, methods further include introducing air bubbles intoany of the regions.

In some examples, methods further include transporting the first fluidor the second fluid in a parallel flow path to each of the regionsbetween the certain ones of the plurality of membranes and transportingthe other of the first fluid or the second fluid in a series flow pathto each of the regions between the other ones of the plurality ofmembranes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration depicting perpendicular flow paths of aseparation system, according to some embodiments.

FIG. 2 is a top down view of a spacer plate of a separation system,according to some embodiments.

FIG. 3A is a cross-sectional view of a spacer plate of a separationsystem along a first axis, according to some embodiments.

FIG. 3B is a cross-sectional view of a spacer plate of a separationsystem along a second axis, according to some embodiments.

FIG. 4 is an isometric view of a membrane plate assembly of a separationsystem, according to some embodiments.

FIG. 5 is an isometric view of multiple membrane plate assembliesarranged in a stack, according to some embodiments.

FIG. 6 is an isometric view of the multiple membrane plate assemblies ofFIG. 5 showing bonding between each membrane plate assembly, accordingto some embodiments.

FIG. 7 is an isometric view of the multiple membrane plate assembly ofFIG. 5 showing a channel provided by stacking the membrane plateassembly, according to some embodiments.

FIG. 8 is a broken cross-sectional view of a separation system along afirst axis, according to some embodiments.

FIG. 9 is a broken cross-sectional view of a separation system along asecond axis, according to some embodiments.

FIG. 10 is a top down view of a spacer plate of a separation system,according to some embodiments.

FIG. 11A is a cross-sectional view of a spacer plate of a separationsystem along a first axis, according to some embodiments.

FIG. 11B is a cross-sectional view of a spacer plate of a separationsystem along a second axis, according to some embodiments.

FIG. 12 is an isometric view of a membrane plate assembly of aseparation system, according to some embodiments.

FIG. 13 is a cross-sectional view of a membrane plate assembly of aseparation system, according to some embodiments.

FIG. 14 is a sectional view of a separation system, according to someembodiments.

FIG. 15 is the sectional view of FIG. 14 showing bonding betweenmultiple membrane plate assemblies of the separation system along afirst axis, according to some embodiments.

FIG. 16 is the sectional view of FIG. 14 showing bonding betweenmultiple membrane plate assemblies of the separation system along asecond axis, according to some embodiments.

FIG. 17 is a cross-sectional view of a separation system along a firstaxis, according to some embodiments.

FIG. 18 is a cross-sectional view of a separation system along a secondaxis, according to some embodiments.

FIG. 19 is an isometric view of a separation system showing flow pathswithin the separation system, according to some embodiments.

FIG. 20 is an isometric view of a separation system, according to someembodiments.

FIG. 21A is cross-sectional view of a separation system stacked inparallel, according to some embodiments.

FIG. 21B is a cross-sectional view of a separation system stacked inseries, according to some embodiments.

FIG. 21C is a cross-sectional view of a separation system stacked in acombination of series and parallel, according to some embodiments.

FIG. 22A is an isometric view of a nipple of a separation system,according to some embodiments.

FIG. 22B is a top down view of a closed nipple, according to someembodiments.

FIG. 22C is a cross-sectional view of a closed nipple, according to someembodiments.

FIG. 22D is a top down view of an open nipple, according to someembodiments.

FIG. 22E is a cross-sectional view of an open nipple, according to someembodiments.

FIG. 23 is an isometric view of a separation system, according to someembodiments.

FIG. 24 is an isometric view of a skid of membrane elements, accordingto some embodiments.

DETAILED DESCRIPTION

Certain details owe set forth below to provide a sufficientunderstanding of embodiments of the invention. However, it will be clearto one skilled in the art that embodiments of the invention may bepracticed without various of these particular details. In someinstances, well-known chemical structures, chemical components,molecules, materials, manufacturing components, control systems,electronic components, timing protocols, and software operations havenot been shown in detail in order to avoid unnecessarily obscuring thedescribed embodiments of the invention.

Disclosed herein are example embodiments of systems, apparatuses andmethods for forward osmosis (FO), pressure retarded osmosis (PRO),membrane distillation (MD), heat exchange membranes, evaporatormembranes, contact membranes, condenser membranes, and absorbermembranes, or generally any separation process. Examples include plateand frame separation elements adapted for use in four port separationwhere two flow paths may be used. Plate and frame separation elementsmay achieve low cost, high packing-density and high yield packaging.Four port separation is generally used herein to refer to separationinvolving two separate flow paths such that not all permeate passingthrough the membrane contributes to an exiting stream. Instead, a firstfluid stream may be provided along a first fluid path and a second fluidstream may be provided along a second fluid path. The term four portseparation is not intended to limit the number of ports which may befound on any particular element or separation system, although in someexamples four ports may in fact be used.

FIG. 1 is an illustration depicting perpendicular flow paths of aseparation system, according to some embodiments. Example membraneelements described herein may utilize stacked membrane layers.Membranes, e.g. membrane 113 may be separated from other membranes by aflow spacer. A fluid flow path may enter in one or more points on oneside of the membrane stack and may exit in one or more points on aseparate side of the stack. Separation may be maintained between fluidflows on opposite sides of a membrane. This may be achieved in someexamples without the need for a glue-line in the middle of two membranelayers (e.g. an envelope), resulting in an improved flow path in someexamples. The one or more openings may be provided along a substantialportion of the edges of the membrane plate assemblies. Thus, the one ormore openings may be the same width as the flow path, therebyfacilitating a uniform velocity across the membrane plate assemblies inthe stack.

By providing for perpendicular flow—e.g., a draw fluid flowing in afirst direction 112 parallel to the plane of one side of a membrane anda feed fluid flowing in a second direction 111, generally perpendicularto the first direction 112 on another side of the membrane—generally theentire membrane surface may be involved in fluid transfer (e.g. forwardosmosis). Orthogonal flow may allow inlet and outlet manifolds toencompass the entire width of the flow path, leading to more uniformlydistributed flows. This may avoid ‘dead zones’ associated with otherfluid flow arrangements where the draw and feed fluids may not haveuniform flow on either side of the entire membrane surface. Other fluidflow arrangements may also have higher head loss, resulting in lowerperformance of the separation system. The advantage of orthogonal flowmay be provided for a ratio of the first fluid flow length to the secondfluid flow length between 2:1 and 1:2 in some examples. Generally,orthogonal or perpendicular flow may refer to at least two flowsoriented substantially 90 degrees with respect to one another such thatan area of the membrane having different fluids on opposite sides may bemaximized. Several embodiments of a flow path for a separation systemmay be used. In some examples, the fluid flow path and associatedcomponents flowing between two membrane layers (e.g. inside a membraneenvelope) may be a draw fluid, and the fluid flow path and associatedcomponents on an opposite side of the two membrane layers (e.g. outsidethe membrane envelope) may be a feed fluid. It will be understood thatin some examples the opposite may be the case. Fluid flow paths may beprovided over rectangular or square membrane layers where the draw fluidflow path enters along one edge, flows through the region betweenmembranes to another (e.g. opposite) edge, as will be described below.It will be understood that membranes may be in other shapes, for example5-sided, 6-sided, 8-sided, or circular shapes. The feed flow path 111may be separated from the draw flow path 112 and can be co-current,counter-current, orthogonal-current or anything in between. Separatedflow paths generally refer herein to flow paths which do not allow forfluid flow between the two paths (e.g. fluidically isolated paths),although in some examples some amount of mixing flows may occur that isnot significant to the overall separation being performed. In someexamples, the flows may separate the membranes of a stack, preventing orreducing the occurrence of the membranes clinging to one another. Bothfeed flow paths 111 and draw flow paths 112 within the separation systemmay be configured independently of one another in parallel, series or acombination of parallel and series. At the membrane surface, the drawand feed flow paths may be in cross flow, with velocities with respectto the membrane surface orthogonal to one another.

FIG. 2 is a top down view of a spacer plate 100 of a separation system,according to some embodiments. The spacer plate 100 may include aspacing region. In some examples, the spacing region may include by aseparating sheet 108. In some examples, the spacing region may includean inner membrane assembly, as will be described below. The separatingsheet 108 may be formed from an injection molded plastic, a wovenmaterial, or any sufficiently flat material that maintains the flow pathinside the region between two membranes (e.g. inside an envelope). Theseparating sheet 108 may include features 109 on one or both sides. Thefeatures 109 may include protrusions, cavities, textures, orcombinations thereof. The features 109 may be in contact with an uppermembrane and/or a lower membrane in a flow path across the spacingregion, as will be described below. The features 109 may createturbulence in the flow path across the spacing region Although thespacer plate 100 depicted is square, it will be understood that othergeometries may be used in other examples, including geometries havingthree, four, five, six, or more sides or being round.

The spacer plate 100 may include one or more openings to facilitatefluid flow through or across the separation system. The one or moreopenings may assist in defining flow paths within the separation system.The fluid flow paths may be in parallel, series or a combination ofparallel and series between adjacent membrane assemblies in a stackedsystem. With fluid flow paths in parallel, each membrane plate assemblymay share a common opening and the fluid flow may be divided among themembrane plate assemblies. This may achieve a shortest possible flowpath and lowest head losses. With fluid flow paths in series (e.g.serpentine), each membrane plate assembly may encompass the entire fluidflow rate. This may generally achieve the highest possible fluidvelocity. Two separate fluid flow paths may be provided in this mannerto facilitate the flow of two different fluids, for example a draw fluidand a feed fluid. In some examples, the two separate fluid flow pathsmay be provided with different combinations of series and parallel fluidflow paths. In some examples, the two separate fluid flow paths may beorthogonal to one another.

In some examples, the one or more openings may include an inlet openingand an outlet opening for a first fluid, for example a draw fluid. Morethan one inlet or outlet opening may be provided for the first fluid. Insome examples, the inlet opening and the outlet opening may be on theopposite edges of the spacer plate 100 so as to facilitate flow of thefirst fluid in a first direction across the spacer plate. The inletopening and the outlet opening may be in fluid communication withregions between the membrane plate assemblies of the separation system.In some examples, the spacer plate 100 may be in a first orientation,and the inlet opening may be opening 102 and the outlet opening may beopening 104. In some examples, the spacer plate may be in a secondorientation, and the inlet opening may be opening 104 and the outletopening may be opening 102. In some examples, the second orientation maybe a 180° rotation about a third axis through the thickness of thespacer plate 100 (e.g., in plane) from the first orientation. In someexamples, elements described herein may include a stack of membraneplate assemblies, with adjacent membrane plate assemblies in the stackhaving alternating orientations. In some examples the membranes bondedto the spacer plate 100 may have a staggered position with respect toone another. For example, the locations at which membranes are bonded toopposite sides of the spacer plate may not be the same (e.g. not ondirectly opposite locations on the spacer plate). In some examples, thelocation at which the membrane is bonded to the spacer plate isoff-center such that when adjacent spacer plates are placed in differentorientations in a stack (e.g. rotated 180 degrees with respect to oneanother), adjacent membranes in the stack may be staggered relative toone another. In this manner, flow paths may be defined by a combinationof adjacent membrane plate assemblies, while allowing the spacer platesto be formed without the need for trapped features (e.g. the spacerplates may be injection molded). Although some examples described hereinmay refer to certain features, such as opening 102, as an inlet openingand may refer to other features, such as opening 104, as an outletopening, it is to be understood that the openings on spacer plates andother flow paths described herein, such as opening 102 and opening 104,may be either an inlet or an outlet depending on the orientation of thespacer plate or configuration of the flow path.

In some examples, the inlet opening, for example opening 102, may be influid communication with the regions between the membrane plateassemblies by a first conduit, for example conduit 105, that transportsthe first fluid to a second conduit, for example conduit 106, that leadsinto the flow path across the spacing region 108. So, for example, theopening 102 may form a fluid manifold when in a stack with multiplespacer places. The opening 102 may be in fluid communication withopenings 105 and 106 which may allow fluid from the manifold region topass under a portion of the spacer plate and enter, at opening 106, aregion between the spacer plate and membranes bonded to the spacerplate. After traveling across the spacing region, the first fluid mayexit the spacer plate 100 through a third conduit, for example conduit107, that may be in fluid communication with the outlet opening, forexample 104. In some examples, the inlet opening and/or the outletopening may be in fluid communication with one or more fluid ports, aswill be described below. Similarly, the one or more openings may includean inlet opening, for example opening 101, and an outlet opening, forexample opening 103, for a second fluid, for example a draw fluid. Theinlet opening and outlet opening for the second fluid may be ondifferent edges with respect to the inlet opening and outlet opening forthe first fluid, and opposite with respect to one another. The openings101 and 103 may form another conduit when stacked with other spacerplates, and may be in fluidic communication with regions between theadjacent membrane plate assemblies in the stack. For example, fluidentering the opening 101 (or 103) may be able to pass between an uppermembrane of the spacer plate 100 and a lower membrane of a spacer platestacked above the spacer plate 100. Fluid entering the opening 101 (or103) may traverse the region between spacer plates in the direction from101 to 103 (or vice versa). This arrangement may facilitate a flow pathfor the second fluid that is orthogonal to the flow path for the firstfluid.

Accordingly, examples of spacer plates described herein, including thespacer plate 100 of FIG. 2 may include a first opening which is in fluidcommunication with a region between membranes bonded to the spacerplate. Example spacer plates may further include a second opening whichmay be in fluid communication with a region between adjacent plateassemblies when the plate assemblies are stacked.

In some examples, the one or more fluid ports may be fitted withinterconnects to define a fluid connection between an upper and lowermembrane element. In some examples, the interconnects may includenipples 2800 that may direct a fluid in a desired manner. As shown inFIG. 22, a nipple 2800 may be shaped to fit within a fluid port of themembrane element. The nipples 2800 may be coupled to the membraneelements using one or more sealing elements 2803, for example O-rings.In some examples, there may be one or more sealing elements 2803 coupledto both an upper membrane element and a lower membrane element. A closedinterconnect, for example closed nipple 2802 shown in FIGS. 22B and 22C,may block the opening separating a first membrane element from a secondmembrane element such that fluid cannot pass through from the firstmembrane element to the second membrane element. An open interconnect2801, for example open nipple 2801 shown in FIGS. 22A, 22 b, and 22C,may include a channel that allows for fluid communication through theopening separating a first membrane element from a second membraneelement such that fluid may pass through from the first membrane elementto the second membrane element. By connecting two or more elements inparallel, these interconnects may be used to configure the elements inparallel (FIG. 21A), series (FIG. 21B) or a combination of series andparallel (FIG. 21C). The first flow path and the second flow path may beconfigured independently. In some examples the first flow path may beconfigured in parallel while the second flow path is configured inseries. In this manner, a series flow, a parallel flow, or combinationsthereof may be established between a stack of membrane elements.

During osmotic flow, membrane flux may be significantly reduced byconcentration polarization (CP). Examples of separation systemsdisclosed herein may increase membrane flux by reducing concentrationpolarization. Membrane flux is generally proportional to the effectiveosmotic driving force. The osmotic driving force may be dissipated byCP, for example internal CP or external CP. Internal CP may be afunction of a support layer of the membrane and the diffusion of thedraw solute. The internal CP generally remains relatively constant withrespect to the spacer plate geometry. External CP may exist within aboundary layer outside of the membrane thickness. External CP may bemitigated through adequate mixing in some examples.

Reduced CP may be achieved by using a spacer plate formed of injectionmolded plastic parts or stamped out of another material. This may allowfor flexibility in spacer plate geometry as many shapes and surfacetextures can be molded with no or minimal increase to part cost. In thismanner, the fabrication of an optimized spacer plate surface may beachieved with no or limited increase to part cost. An optimized spacerplate may advantageously mitigate external CP by increasing draw fluidturnover while maintaining a low head loss. This may reduce the amountof dilutive external CP, thereby increasing the effective osmoticdriving force.

FIG. 3A is a cross-sectional view of a spacer plate 100 of a separationsystem along a first axis, according to some embodiments. FIG. 3B is across-sectional view of a spacer plate of a separation system along asecond axis, according to some embodiments. The spacer plate 100 mayinclude a first surface having one or more bonding areas. The bondingareas may be generally along the perimeter of the spacer plate 100. Insome examples, the bonding areas may be where an element of theseparation system, for example a membrane or another spacer plate 100,may be coupled to the spacer plate 100. The element of the separationsystem may be coupled to the spacer plate 100 using an adhesive (e.g.pressure sensitive adhesive), by welding (e.g., thermal, solvent, orultrasonic weld), a glued line, a fold in material, and/or any otherknown mechanism. The coupling may provide a fluidic seal. In someexamples, a first bonding area of the first surface of the spacer plate100 may include surfaces 210, 212, 214 and 216. In some examples, asecond bonding area of the first surface of the spacer plate 100 mayinclude surfaces 220 and 233, and may be staggered (e.g., asymmetricallyarranged) about the second axis. The first and second bonding areas maybe used to couple a first spacer plate 100 and a second spacer plate100. The spacer plate 100 may also include bonding areas for couplingthe spacer plate 100 with a membrane 302. These bonding areas mayinclude surfaces 222 and 231, which may be staggered about the secondaxis, and surfaces 234 and 236, which may be symmetrical about the firstaxis.

The spacer plate 100 may include a second surface having similar bondingareas as the bonding areas on the first surface. The second surface maybe located on an opposite side of the spacer plate 100 relative to thefirst surface. The second surface of a first spacer plate 100 may bondto the first surface of a second spacer plate 100, as will be describedbelow. In some examples, a first bonding area of the second surface ofthe spacer plate 100 may include surfaces 211, 213, 215 and 217. Insonie examples, a second bonding area of the second surface of thespacer plate 100 may include surfaces 219 and 230. The spacer plate 100may also include bonding areas for coupling the spacer plate 100 with amembrane 303. These bonding areas may include surfaces 219 and 230,which may be staggered about the second axis, and surfaces 235 and 237,which may be symmetrical about the first axis.

FIG. 4 is an isometric view of a membrane plate assembly of a separationsystem, according to some embodiments. A membrane plate assembly mayinclude a spacer plate 100, a first membrane 302 (also referred toherein an “upper membrane”), a second membrane 303 (also referred toherein as a “lower membrane”), and a spacer sheet 304. The firstmembrane 302 may be bonded to a first surface of the spacer plate 100along the perimeter of the first membrane 302. The second membrane 303may be bonded to a second surface of the spacer plate 100 along theperimeter of the second membrane 303. In some examples the firstmembrane may form a membrane to plate bond on surfaces 222, 231, 234,and 236 around the entire perimeter of the membrane. The second membrane303 may form a membrane to plate bond on surfaces 219, 230, 235 and 237around the entire perimeter of the membrane. In some examples, thesupport side (backside) of the membranes may be bonded to the spacerplate 100. In this manner, the membrane plate assembly may operate in askin to feed mode (e.g., FO mode). In some examples, the skin side(frontside) of the membranes may be bonded to the spacer plate 100. Inthis manner, the membrane plate assembly may operate in a skin to saltmode (e.g., PRO mode).

The first membrane 302 and the second membrane 303 may be formed from avariety of membrane materials including, but not limited to, celluloseacetate, polyacrylonitrile, meta-aramides e.g., Nomex®) and/orpara-aramids (e.g., Kevlart®), acrylate-modified poly(vinylidenefluoride), polyamide or thin film composite (TFC) with a polysulfone,polyamide, polyethersulfone, polyacrylonitrile, meta-aramides (e.g.,Nomex®) and/or para-aramids (e.g., Kevlar®), acrylate-modifiedpoly(vinylidene fluoride) polymer support layer, or any membranesuitable for forward osmosis. Different types of membranes may be used,for example reverse osmosis membranes, ultrafiltration membrane,membrane distillation membranes, or pressure retarded osmosis membranes.

The spacer sheet 304 may be formed from a material that supports astructured flow path between the two layers of membrane outside theenvelope. The spacer sheet 304 may be implemented using a wovenmaterial, a molded plastic material, or any sufficiently flat materialthat maintains the flow path outside the envelope. The spacer sheet 304may be positioned on a side of a membrane opposite the spacer plate 100.The spacer sheet 304 may be coupled to the spacer plate 100 along itsperimeter to a bonding area of the spacer plate 100 or a membrane. Thecoupling may be achieved using methods including, but not limited to,gluing, welding, mechanically fastening, or using an adhesive. In someexamples, the spacer sheet 304 may be coupled to a first spacer plate100 on surfaces 219 and 230 and a second spacer plate 100 on surfaces222 and 231. The spacer sheet 304 is optional and may not be included inall examples. When the spacer sheet 304 is absent, a void may be presentin the region, allowing fluid flow.

Referring to FIG. 4, in some examples, a first fluid may enter fluidmanifolds on the right or left-hand side of the Figure, and access theregion between membranes 302 and 303 through, for example, the openings105 and 107. A second fluid may enter fluid manifolds shown on the upperor lower side of the Figure, and access regions between adjacentmembrane plate assemblies (e.g. outside of the membranes 302 and 303).The membranes 302 and 303 may be bonded to the plate across the width ofthe spacer plate shown in FIG. 4, such that fluid from the manifoldsshown on the upper and lower edges of the spacer plate may be isolatedfrom the region between the membranes 302 and 303.

FIG. 5 is an isometric view of multiple membrane plate assembliesarranged in a stack, according to some embodiments. Once stacked, theone or more openings of the spacer plates 100 may be arranged such thatthe inlets and outlets 101, 102, 103, and 104 may align with one anotherto form a unified manifold. In some examples, the one or more openingsaligned with one another may allow a fluid to be in fluid communicationwith multiple conduits of the spacer plates 100 of each of the membraneplate assemblies in the stack. In this manner, parallel flow may beachieved. In some examples, the openings of one of the spacer plates 100may be blocked to force all of the fluid to pass through the conduits ofthat spacer plate 100. In this manner, series flow may be achieved.

The spacer plates 100 may be stacked by coupling the plates together attheir bonding areas, as described above. Perimeter plate to platecoupling may be achieved by joining surface 210 of a lower plate 1051(See FIG. 8) to surface 213 of an upper plate 1050 and joining surface212 of the lower plate 1051 to surface 211 of the upper plate 1050 andjoining surface 214 of the lower plate 1051 to surface 217 of the upperplate 1050 and joining surface 216 of the lower plate 1051 to surface215 of the upper plate 1050. Joining the surfaces of the spacer plates100 in this manner may result in an alternating arrangement of thespacer plates 100 in which each spacer plate 100 is rotated 180° inplane with respect to the spacer plate 100 adjacent to it. Note that theasymmetric design of the spacer plate 100 facilitates formation of flowpaths using a single type of plate and without the need to have trappedfeatures on the spacer plate 100 (e.g. the spacer plate 100 may be aninjection molded part). Perimeter plate to plate coupling may separatethe fluid flow paths from the outside world. In addition, internal plateto plate coupling may be achieved by joining surface 233 of the lowerplate 1051 to surface 219 of the upper plate 1050 and surface 220 of thelower plate 1051 to surface 230 of the upper plate 1050. Internal plateto plate coupling may separate the first fluid flow path and the secondfluid flow path. Both the perimeter plate to plate coupling and theinternal plate to plate coupling may include joining the plates alongthe entire width of the spacer plate 100.

FIG. 6 is an isometric view of the multiple membrane plate assemblies ofFIG. 5 showing bonding between each membrane plate assembly, accordingto some embodiments. The membrane plate assemblies in the stack may bein alternating orientations with respect to one another to allow theplate to be injection molded. A staggered second bonding area (internalseal separating draw from feed) may be achieved by an asymmetricarrangement of surfaces, as shown in FIGS. 3A and 3B. The asymmetricarrangement of surfaces of the spacer plate 100 may provide innerplate-to-plate bonding areas on both sides of the spacer plate 100 thatare the same distance apart, but positioned at different points alongthe spacer plate 100. In some examples, the spacer plates 100 mayalternate in orientation to achieve the staggered membrane arrangement.For example, the distance between surface 220 and surface 233 may be thesame as the distance as the distance between surface 219 and surface230. This may allow for surface 220 of a first plate to join withsurface 230 of a second plate while surface 233 of the first plate joinswith surface 219 of the second plate. As shown in FIG. 3A, surface 220may not be aligned with surface 219 and surface 233 may not be alignedwith surface 230. This offset may create a staggered arrangement.Continuing with the previous example, surface 219 of the first plate mayjoin with surface 233 of a third plate and surface 230 of the firstplate may join with surface 220 of the third plate. The second plate andthird plate may be in alignment because the first plate may have beenrotated 180° with respect to the second plate and the third plate mayhave rotated 180° about the third axis with respect to the first plate.By using an asymmetric arrangement of surfaces and alternating themembrane plate assemblies, it may be feasible to injection mold thespacer plates 100 out of one piece while maintaining a desired number ofopenings, for example four openings, and desired number of distinct flowpaths, for example two distinct flow paths. In this manner, trappedfeatures may be avoided, and only one type of plate may be requiredthroughout the membrane element, and only one type of plate may berequired throughout the membrane element, thereby enhancingmanufacturing efficiency and packing density.

FIG. 7 is an isometric view of the multiple membrane plate assemblies ofFIG. 5 showing a channel 900 provided by stacking the membrane plateassemblies, according to some embodiments. Channels 900 may beassociated with a first fluid or a second fluid. Once stacked, an arrayof channels 900 for a first fluid may be on two sides of the stack andan array of channels 900 for a second fluid may be on another two sidesof the stack. In some examples, the two sides that the array of channels900 for each fluid is located are opposite to one another.

FIG. 8 is a broken cross-sectional view of a separation system along afirst axis, according to some embodiments. In some examples, a firstfluid may enter from the inlet opening, for example the first inletmanifold 1054 formed by openings 102 and 104, of the spacer plate 100through an inlet channel 900 associated with the first fluid, and into achannel 1041 formed by surface 1232 of an upper spacer plate 1052 andsurface 1218 of a lower spacer plate 1051. The flow of the first fluidmay split into two parts at point 238 shown in FIG. 3A. In someexamples, the two parts may be equal halves. The first fluid may thenenter an upper channel 1042 and a lower channel 1043. The upper channel1042 may be formed by surface 229 of an upper plate 1050 and an uppermembrane 302 of the upper plate 1050. The lower channel 1043 may beformed by surface 221 of a lower plate 1051 and a lower membrane 303 ofthe lower plate 1051. The upper channel 1042 may be coupled to an innerchannel 1044 formed by the upper membrane 302 of the upper plate 1050and the lower membrane 303 of the upper plate 1050. The lower channelmay be coupled to another inner channel 1045 formed by the uppermembrane 302 of the lower plate 1051 and the lower membrane 303 of thelower plate 1051.

The fluid traveling through the inner channel 1044 may then split intotwo parts at point 228 of the upper plate 1050. A portion may enter anupper channel 1046 and a portion may enter a lower channel 1047. Theupper channel 1046 may be formed by surface 227 of the spacer plate 100and the upper membrane 302 of the upper plate 1050. The lower channel1047 may be formed by surface 226 of the spacer plate 100 and the lowermembrane 303 of the upper plate 1050. The flows from both the upperchannel 1046 and the lower channel 1047 may travel across the membraneplate assembly. At point 223 of the spacer plate 100, the flowstraveling through the upper channel 1046 and the lower channel 1047 mayrecombine and exit through an outlet channel 900 associated with thefirst fluid to the outlet opening, for example the first outlet manifold1055 formed by opening 102 and 104, of the spacer plate 100.

FIG. 9 is a broken cross-sectional view of a separation system along asecond axis, according to some embodiments. A second fluid may enterfrom an inlet opening, for example the second inlet manifold 131 formedby opening 101 and 103, of the spacer plate 100 through an inlet channel900 associated with the second fluid. The second fluid may betransported into the spacer sheet 304 of a lower plate 1163 trapped in achannel formed by surface 234 of the lower plate 1163 and surface 237 ofan upper plate 1162. The second fluid may flow across the membrane plateassembly. The second fluid may exit through an outlet channel 900associated with the second fluid and then exit through the outletopening, for example the second outlet manifold 133 formed by opening101 and 103, of the spacer plate 100.

FIG. 10 is a top down view of a spacer plate 1200 of a separationsystem, according to some embodiments. It will be understood that spacerplate 1200 operates similarly to spacer plate 100 described above.Spacer plate 1200 may enhance the packing density of the membrane plateassemblies by minimizing dead space resulting from non-membranematerials. Instead of a separating sheet 1208 in the spacing region,spacer plate 1200 may include an internal membrane assembly 1208 in itsspacing region. Thus, dead volume resulting from the separating sheet108 may be avoided. In addition to improving the packing density of themembrane plate assemblies, this arrangement may increase the membranesheet area by increasing the overall dimensions of the spacer plate1200. It may be possible to increase the overall dimensions of thespacer plate 1200 while still satisfying minimum thickness and maximumarea manufacturing requirements. The spacer plate 1200 may also reducethe plate cost per membrane area since the volume of material, forexample plastic, that may be required to form the spacer plate 1200 maybe reduced. The spacer plate 1200 may include no trapped features, whichmay allow it to be molded in a simple two part mold. Although the spacerplate 1200 depicted is square, it will be understood that othergeometries may be used in other examples, including geometries havingthree, four, five, six, or more sides or being round.

The spacer plate 1200 may include an inlet opening, for example opening1202, and an outlet opening, for example opening 1204, for a firstfluid, for example a draw fluid. More than one inlet or outlet openingmay be provided for the first fluid. In some examples, the inlet openingand the outlet opening may be on the opposite edges of the spacer plate1200 so as to facilitate flow of the first fluid in a first directionacross the spacer plate. The inlet opening and the outlet opening may bein fluid communication with regions between the membrane plateassemblies of the separation system. In some examples, the spacer plate1200 may be in a first orientation, and the inlet opening may be opening1202 and the outlet opening may be opening 1204. In some examples, thespacer plate may be in a second orientation, and the inlet opening maybe opening 1204 and the outlet opening may be opening 1202. In someexamples, the second orientation may be a 180° rotation of the spacerplate 1200 from the first orientation. Although some examples may showopening 1202 as an inlet opening and opening 1204 as an outlet openingor vice versa, it will be understood that opening 1202 and opening 1204may be either an inlet or an outlet depending on the orientation of thespacer plate 1200.

In some examples, the inlet opening may be in fluid communication withthe regions between the membrane plate assemblies by a first conduit,for example conduit 1205, that transports the first fluid to a secondconduit, for example conduit 1206, that leads into the flow path acrossthe spacing region 1208. After traveling across the spacing region, thefirst fluid may exit the spacer plate through a third conduit, forexample conduit 1207, that may be in fluid communication with the outletopening. In some examples, the inlet opening and/or the outlet openingmay be in fluid communication with one or more fluid ports, as will bedescribed below.

In some examples the one or more openings may include an inlet opening,for example opening 1201, and an outlet opening, for example opening1203, for a second fluid, for example a feed fluid. More than one inletor outlet may be provided for the second fluid. In some examples, theinlet opening and the outlet opening may be on the opposite edges of thespacer plate 1200 so as to facilitate flow of the second fluid in a inan orthogonal direction with respect to the first fluid across thespacer plate 1200. In some examples, the spacer plate 1200 may be in afirst orientation, and the inlet opening may be opening 1202 and theoutlet opening may be opening 1204. In some examples, the spacer platemay be in a second orientation, and the inlet opening may be opening1204 and the outlet opening may be opening 1202. In some examples, thesecond orientation may be a 180° rotation of the spacer plate 1200 fromthe first orientation. Although some examples may show opening 1202 asan inlet opening and opening 1204 as an outlet opening or vice versa, itwill be understood that opening 1202 and opening 1204 may be either aninlet or an outlet depending on the orientation of the spacer plate1200.

In some examples, the inlet opening may be in fluid communication withthe regions outside of the regions between the membranes and the innermembrane assembly 1208 by a first conduit, for example conduit 1212. Thesecond fluid may exit the membrane plate assembly through a secondconduit, for example conduit 1211. In some examples, the inlet openingand/or the outlet opening may be in fluid communication with one or morefluid ports, as will be described below.

In some examples, the one or more openings may be fitted withinterconnects to define a parallel flow path or a series flow path. Theinterconnects may block the opening such that fluid cannot pass throughin order to facilitate a series flow. The interconnects may allow flowthrough an opening to the spacer plate below in order to facilitate aparallel flow. In this manner, a series flow, a parallel flow, orcombinations thereof may be established between a stack of spacerplates. In some examples, the interconnects may include nipples that maydirect a fluid in a desired manner.

FIG. 11A is a cross-sectional view of a spacer plate 1200 of aseparation system along a first axis, according to some embodiments.FIG. 11B is a cross-sectional view of a spacer plate 1200 of aseparation system along a second axis, according to some embodiments.The spacer plate 1200 may include a first surface having one or morebonding areas. The bonding areas may be generally along the perimeter ofthe spacer plate 1200. In some examples, the bonding areas may be wherean element of the separation system, for example a membrane or anotherspacer plate 1200, may be coupled to the spacer plate 1200. The elementof the separation system may be coupled to the spacer plate 1200 usingan adhesive (e.g. pressure sensitive adhesive), by welding (e.g.,thermal or ultrasonic weld), a glued line, a fold in material, and/orany other known mechanism. The coupling may provide a fluidic seal. Insome examples, a first bonding area of the first surface of the spacerplate 1200 may include surfaces 1320, 1342, 1350 and 1367. In someexamples, a second bonding area of the first surface of the spacer plate1200 may include surfaces 1325 and 1340, and may be staggered (e.g.,asymmetrically arranged) about the second axis. The first and secondbonding areas may be used to couple a first spacer plate 1200 and asecond spacer plate 1200.

The spacer plate 1200 may include a second surface having similarbonding areas to the first surface. The second surface may be located onan opposite side of the spacer plate 1200 relative to the first surface.The second surface of the first spacer plate 1200 may bond to the firstsurface of a second spacer plate 1200 as will be described below. Insome examples, a first bonding area of the second surface of the spacerplate 1200 may include surfaces 1321, 1343, 1351 and 1368. In someexamples a second bonding area of a second surface of the spacer plate1200 may include surfaces 1323 and 1337, and may be staggered(asymmetrically arranged) about the second axis of spacer plate 1200.

The spacer plate 1200 may also include bonding areas for coupling thespacer plate 1200 with a membrane 1403. These bonding areas may includesurfaces 1327 and 1338, which may be staggered about the second axis,and surfaces 1356 and 1366, which may be staggered about the first axis.The spacer plate 1200 may also include bonding areas for coupling thespacer plate 1200 with a membrane 1406. These bonding areas may includesurfaces 1329 and 1333, which may be symmetrical about the second axis,and surfaces 1358 and 1364, which may be staggered about the first axis.The spacer plate 1200 may also include bonding areas for coupling thespacer plate 1200 with a membrane 1408. These bonding areas may includesurfaces 1330 and 1334, which may be symmetrical about the second axis,and surfaces 1355 and 1361, Which may be staggered about the first axis.The spacer plate 1200 may also include bonding areas for coupling thespacer plate 1200 with a membrane 1410. These bonding areas may includesurfaces 1323 and 1337, which may be staggered about the second axis,and surfaces 1353 and 1363, which may be staggered about the first axis.

FIG. 12 is an isometric view of a membrane plate assembly of aseparation system, according to some embodiments. The membrane plateassembly may include the spacer plate 1200, a spacer sheet 1402 (alsoreferred to herein as “first spacer sheet”), a first membrane 1403, anda second membrane 1410. The spacer sheet 1402 may be similar to thespacer sheet 304 described above. In addition, the first membrane 1403(also referred to herein as “upper outer membrane”) and the secondmembrane 1410 (also referred to herein as “lower outer membrane”) may besimilar to the first membrane 302 and the second membrane 303 describedabove. The membrane plate assembly may also include an inner membraneassembly 1208. The inner membrane assembly may be a multi-layer assemblyincluding a second spacer sheet 1407, a third membrane 1406 (alsoreferred to herein as “upper inner membrane”) on a first side of thesecond spacer sheet 1407, a third spacer sheet 1405 on a side of thethird membrane 1406 opposite the second spacer sheet 1407, a fourthmembrane 1408 (also referred to herein as “lower inner membrane) on asecond side of the second spacer sheet 1407, and a fourth spacer sheet1409 on a side of the fourth membrane 1408 opposite the second spacersheet 1407. In some examples, the first membrane 1403, the secondmembrane 1410, the third membrane 1406 and the fourth membrane 1408 maybe forward osmosis membranes.

FIG. 13 is a cross-sectional view of a membrane plate assembly of aseparation system, according to some embodiments. FIG. 13 shows therelatively small amount of space occupied by the spacer plate 1200 andthe relatively large amount of space occupied by the membranes andspacers. The high proportion of spacers and membranes relative to deadspace from the spacer plate 1200 results in a higher packing density anda higher level of separation that may be carried out in a given amountof space.

The lower surface of the first spacer sheet 1402 may be in contact withthe upper surface of an upper outer membrane 1403 of a lower plate 2184(See FIG. 17). The upper surface of the first spacer sheet 1402 may bein contact with the lower surface of a lower outer membrane 1410 of anupper plate 2171. The upper plate 2171 may separate the upper outermembrane 1403 from the lower outer membrane 1410, and may provide astructured flow path between them. The lower surface of the third spacersheet 1405 may be in contact with the upper surface of the upper innermembrane 1406. The upper surface of the third spacer sheet 1405 may bein contact with the lower surface of the upper outer membrane 1403. Thethird spacer sheet 1405 may separate the upper outer membrane 1403 fromthe upper inner membrane 1406, and may provide a structured flow pathbetween them. The lower surface of the second spacer sheet 1407 may bein contact with the upper surface of the lower inner membrane 1408. Theupper surface of the second spacer sheet 1407 may be in contact with thelower surface of the upper inner membrane 1406. The second spacer sheet1407 may separate the lower inner membrane 1408 from the upper innermembrane 1406, and provide a structured flow path between them. Thelower surface of a fourth spacer sheet 1409 may be in contact with theupper surface of the lower outer membrane 1410. The upper surface of thefourth spacer sheet 1409 may be in contact with the lower surface of thelower inner membrane 1408. The fourth spacer sheet 1409 may separate thelower outer membrane 1410 from the lower inner membrane 1408, andprovide a structure flow path between them.

FIG. 14 is a sectional view of a separation system, according to someembodiments. Like FIG. 13, FIG. 14 shows the relatively small amount ofspace occupied by the spacer plate 1200 and the relatively large amountof space occupied by the membranes and spacers. The membrane plateassemblies may be stacked, whereby one or more openings of the spacerplates 1200 may be arranged to be aligned with one another. Any numberof membrane plate assemblies may be stacked to form an element,including 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 membrane plate assemblies, ormore in other examples. Adjacent membrane plate assemblies in the stackmay have having alternating orientations and may have membranesstaggered in position with respect to one another, as shown in examplesdescribed herein. In some examples, the one or more openings alignedwith one another may allow a fluid to be in fluid communication withmultiple conduits of the spacer plates 1200 of each of the membraneplate assemblies in the stack. In this manner, parallel flow may beachieved. In some examples, the openings of one of the spacer plates1200 may be blocked to force all of the fluid to pass through theconduits of that spacer plate 1200. In this manner, series flow may beachieved.

The spacer plates 1200 may be stacked by coupling the plates together attheir bonding areas, as described above. Perimeter plate to platecoupling may be achieved by joining surface 1320 of a lower plate 2184(See FIG. 17) to surface 1343 of an upper plate 2171 and joining surface1342 of the lower plate 2184 to surface 1321 of the upper plate 2171.Joining the surfaces of the spacer plates 1200 in this manner may resultin an alternating arrangement of the spacer plates 1200 in which eachspacer plate 1200 is rotated 80° about a third axis with respect to thespacer plate 1200 adjacent to it, Perimeter plate to plate coupling mayseparate the fluid flow paths from the outside world. In addition,internal plate to plate coupling may be achieved by joining surface 1340of the lower plate 2184 to surface 1323 of the upper plate 2171 andsurface 1325 of the lower plate 2184 to surface 1337 of the upper plate2171. Internal plate to plate coupling may separate the first fluid flowpath and the second fluid flow path. Both the perimeter plate to platecoupling and the internal plate to plate coupling may include joiningthe plates along the entire width of the spacer plate 1200.

FIG. 15 is the sectional view of FIG. 14 showing bonding betweenmultiple membrane plate assemblies of the separation system along afirst axis, according to some embodiments. FIG. 16 is the sectional viewof FIG. 14 showing bonding between multiple membrane plate assemblies ofthe separation system along a second axis, according to someembodiments. The membranes of the membrane plate assemblies in the stackmay be staggered with respect to one another. It may be advantageous tostagger the membranes to improve packing efficiency and due tomanufacturing considerations. Staggering may be achieved by anasymmetric arrangement of surfaces, as shown in FIGS. 11A and 11B. Insome examples, the spacer plates 1200 may alternate in orientation toachieve the staggered arrangement. The asymmetric arrangement ofsurfaces of the spacer plate 1200 may provide inner plate-to-platebonding areas on both sides of the spacer plate 1200 that are the samedistance apart, but positioned at different points along the spacerplate 1200. In some examples, the spacer plates 100 may alternate inorientation to achieve the staggered arrangement. For example, thedistance between surface 1325 and surface 1340 may be the same as thedistance as the distance between surface 1323 and surface 1337. This mayallow for surface 1325 of a first plate to join with surface 1337 of asecond plate while surface 1340 of the first plate joins with surface1323 of the second plate. As shown in FIG. 11A, surface 1325 may not bealigned with surface 1323 and surface 1340 may not be aligned withsurface 1337. This offset may create a staggered arrangement. Continuingwith the previous example, surface 1323 of the first plate may join withsurface 1340 of a third plate and surface 1337 of the first plate mayjoin with surface 1325 of the third plate. The second plate and thirdplate may be in alignment because the first plate may have been rotated180° about a third axis with respect to the second plate and the thirdplate may have been rotated 180° about the third axis with respect tothe first plate. By using an asymmetric arrangement of surfaces andstaggering the membrane plate assemblies, it may be feasible toinjection mold the spacer plates 1200 out of one piece while maintaininga desired number of openings, for example four openings, and desirednumber of distinct flow paths, for example two distinct flow paths. Inthis manner, trapped features may be avoided, thereby enhancingmanufacturing efficiency and packing density.

The upper outer membrane 1403 may form a membrane to plate bond onsurfaces 1327, 1338, 1356, and 1366 of the spacer plate 1200. The upperinner membrane 1406 may form a membrane to plate bond on surfaces 1329,1333, 1358, and 1364 of the spacer plate 1200. The lower inner membrane1408 may form a membrane to plate bon on surfaces 1330, 1334, 1355, and1361 of the spacer plate 1200. The lower outer membrane 1410 may form amembrane to plate bond on surfaces 1323, 1337, 1353, and 1363 of thespacer plate 1200. The membrane to plate bond for the upper outermembrane 1403, the upper inner membrane 1406, the lower inner membrane1408, and the lower outer membrane 1410 may be provided around theentire perimeter of the membrane.

FIG. 17 is a cross-sectional view of a separation system along a firstaxis, according to some embodiments. In some examples, a first fluid,for example a draw fluid, may enter the membrane plate assembly from theinlet opening, for example an inlet manifold 1231 formed by openings1201 and 1203, and travel through an inlet channel associated with thefirst fluid, and into a channel 2172 formed by surface 1339 of an upperplace 2171 and surface 1322 of a lower plate 2184. The fluid flow pathmay be split into two halves at point 1324, whereby it enters an upperchannel 2174 and a lower channel 2185. The upper channel 2174 may beformed by surface 1336 of the upper plate 2171 and the upper outermembrane 1403 of the upper plate 2171. The lower channel 2185 may beformed by surface 1326 of the lower plate 2184 and the lower outermembrane 1410 of the lower plate 2184.

The upper channel 2174 may direct the first fluid to a channel 2175formed by the upper outer membrane 1403 of the upper plate 2171 and thelower outer membrane 1410 of the upper plate 2171. The lower channel2185 may direct the first fluid to a channel 2186 formed by the upperouter membrane 1403 of the lower plate 2184 and the lower outer membrane1410 of the lower plate 2184. The channel 2175 may then split into twohalves at point 1335 of the upper plate 2171, whereby it may enter anupper channel 2176 or a lower channel 2177. The upper channel 2176 maybe formed by surface 1333 of the spacer plate 1200 and the upper outermembrane 1403 of the upper plate 2171. The lower channel 2177 may beformed by surface 1334 of the spacer plate 1200 and the lower outermembrane 1410 of the upper plate 2171.

The upper channel 2176 may direct the first fluid to a channel 2178,which is formed by the upper outer membrane 1403 and the upper innermembrane 1406 of an upper plate 2171, whereby the first fluid may travelthrough the third spacer sheet 1405. The lower channel 2177 may directthe first fluid to a channel 2179, which is formed by the lower outermembrane 1410 and the lower inner membrane 1408 of the upper plate 2171,whereby the first fluid may travel through fourth spacer sheet 1409. Theflows through channel 2178 and channel 2179 may transport the firstfluid across the spacer plate 1200 contacting the membranes. At point1328 of the spacer plate 1200, channel 2178 and channel 2179 recombinead the first fluid may exit through the outlet opening 1203 following asimilar path through the outlet channels. In some examples, the flowentering the outlet opening 1203 may interact with merging flows fromthe upper plate 2173. The upper stream may not meet the lower stream2186 until they have both reached outlet opening, for example outletmanifold 1233 formed by openings 1201 and 1203.

FIG. 18 is a cross-sectional view of a separation system along a secondaxis, according to some embodiments. In some examples, a second fluid,for example a feed fluid, may enter from the inlet opening, for exampleinlet manifold 1232 formed by openings 1202 and 1204, through an inletchannel associated with the second fluid into channel 2202 formed bysurface 1353 of an upper plate 2201 and surface 1366 of a center plate2203, and into channel 2204 formed by surface 1365 of a center plate2203 and surface 1354 of a lower plate 2212. Channel 2204 may split intothree even paths: an upper flow path 2204, a center flow path 2206, anda lower flow path 2213. The upper flow path 2205 may be formed bysurface 1362 and the upper inner membrane 1406 of the center plate 2203.The center flow path 2206 may be formed by surface 1363 of the centerplate 2203 and surface 1356 of the lower plate 2212. The lower flow path2213 may be formed by surface 1326 and the lower inner membrane 1408 ofthe lower plate 2212.

Channel 2202 may direct the second fluid into a channel formed by thelower outer membrane 1410 of the upper plate 2201 and the upper outermembrane 1403 of the center place 2203. The second fluid may then flowthrough the first spacer sheet 1402 of the center plate 2203. The upperflow path 2205 may lead to channel 2208, which is formed by the upperinner membrane 1406 and the lower inner membrane 1408 of the centerplate 2203. Channel 208 may direct the second fluid through the secondspacer sheet 1407 of the center plate 2203. Channel 2208 may then directthe second fluid to channel 2209, which may be formed by surface 1357and the lower inner membrane 1408 of the center plate 2203. Channels2207, 2209 and 2210 may then combine in channel 2211, and exit to theoutlet opening, for example outlet manifold 1234 formed by openings 1202and 1204.

The center flow path 2206 may enter channel 2214 formed by the lowerouter membrane 1410 of the center plate 2203 and the upper outermembrane 1403 of the lower plate 2212. Channel 114 may direct the secondfluid through the first spacer sheet 1402 of the lower plate 2212.Channel 2214 may direct the second fluid to the outlet opening.

The lower flow path 2213 may enter channel 2215, which may be formed bythe upper inner membrane 1406 and the lower inner membrane 1408 of thelower plate 2212. Channel 2215 may direct the second fluid through thesecond spacer sheet 1407 of the lower plate 2212. Channels 2215, 2216,and 2217 may then combine n channel 2218, and exit to the outletopening.

FIG. 19 is an isometric view of a separation system showing flow pathswithin the separation system, according to some embodiments. The one ormore openings may direct a fluid from a first side of a membrane plateassembly to a second side of the membrane plate assembly. A flow path ofthe first fluid, for example a draw fluid, may be along a first axis. Insome examples, the first side and the second side may be opposite edgesof the spacer plate 100. For example, a first fluid inlet flow path 2301may direct a first fluid from outside the separation system to the firstinlet manifold 1054 of the separation system, as described above. Thefirst fluid may enter the membrane plate assembly through the inletchannel and flow along a first axis and out through first outletmanifold 1055 of the separation system. A first fluid outlet flow path2302 may direct the first fluid exiting each spacer plate 100 out of theseparation system.

A flow path of the second fluid, for example a feed fluid, may be alonga second axis. In some examples, the second axis may be orthogonal tothe first axis. In some examples, the second axis may be at a differentangle with respect to the first axis. In some examples, the first sideand the second side may be opposite edges of the spacer plate 100. Forexample, a second fluid inlet flow path 2303 may direct a first fluidfrom outside the separation system to the second inlet manifold 131 ofthe separation system, as described above. The first fluid may enter themembrane plate assembly through the inlet channel and flow along asecond axis and out through second outlet manifold 133 of the separationsystem. A second fluid outlet flow path 2304 may direct the second fluidexiting each spacer plate 100 out of the separation system.

In some examples, air bubbles may be introduced, flowing through thefeed flow path, to reduce the propensity of membrane fouling in theseparation system.

FIG. 20 is an isometric view of a membrane element 2400, according tosome embodiments. Assembly of the membrane element 2400 may be completedby adhering a foot plate 2406 and a head plate 2405. The head plate 2405and foot plate 2406 may be sealed, for example, with a mechanical seal,adhesive seal or weld. The foot plate may seal the bottom of themembrane element 2400, The head plate 2405 may provide a sealing surfacefor the one or more openings of the spacer plates and may supplyplumbing options, for example fluid ports. The head plate 2405 may bepositioned at the top of the membrane element 2400, and may include oneor more fluid ports coupled to the one or more openings. A first fluidport 2401 may be provided to receive a first fluid, for example a feedfluid, and transport it to a first inlet manifold 1054 of the separationsystem. A second fluid port 2402 may provide an outlet for first fluidthat has passed through the membrane element 2400 and into the firstoutlet manifold 1055 of the separation system. In some examples, thesecond fluid port 2402 may be located on the foot plate 2406. A thirdfluid port 2403 may be provided to receive a second fluid, for example adraw fluid, and transport it to a second inlet manifold 131 of theseparation system A fourth fluid port 2404 may provide an outlet forsecond fluid that has passed through the membrane element 2400 and intothe second outlet manifold 133 of the separation system. Other ports mayalso be present, or multiple ports used per inlet and outlet in someexamples. FIG. 21A is cross-sectional view of a membrane element 2400stacked in parallel, according to some embodiments. Examples ofseparation systems described herein may maintain a flow path for fourport elements while increasing packing density, increasing yields anddecreasing head losses in some examples. This may result in asubstantially lower head loss due to an improved flow path, in someexamples multiple membrane elements 2400 may be coupled by aligningtheir fluid ports. A top plate first fluid port 2501 may direct a firstfluid to a first fluid port 2401 of the head plate of a first membraneelement 2400. The first fluid may then pass through the first membraneelement 2400. The first fluid may then pass to a membrane element 2400by exiting the first membrane element 2400 through a second fluid port2402 located on the foot plate of the first membrane element 2400. Thesecond fluid port 2402 may be coupled to first fluid port 2401 of asecond membrane element 2400 positioned beneath the first membraneelement 2400. Similarly, the first fluid may pass through a thirdmembrane element 2400. For a parallel configuration, all the first fluidports 2401 and second fluid ports 2402 may be on a first side of eachmembrane element 2400. The first fluid may pass through each membraneelement 2400 in a similar fashion and may be plumbed through a top platesecond fluid port 2502. In some examples, the fluid ports of themembrane elements 2400, top plate, and/or bottom plate may includeinterconnects, for example open nipples 2801 or closed nipples 2802.

A top plate third fluid port 2503 may direct a second fluid to a thirdfluid port 2403 of the head plate of a first membrane element 2400. Thesecond fluid may then pass through the first membrane element 2400. Thesecond fluid may then pass to a second membrane element 2400 by exitingthe first membrane element 2400 through a fourth fluid port 2404 locatedon the foot plate of the first membrane element 2400. The fourth fluidport 2404 may be coupled to the third fluid port 2403 of a secondmembrane element 2400 positioned beneath the first membrane element2400. Similarly, the first fluid may pass through a third membraneelement 2400. For a parallel configuration, all the third fluid ports2403 and fourth fluid ports 2404 may be on a first side of each membraneelement 2400. The second fluid may pass through each membrane element2400 in a similar fashion and may be plumbed through a top plate fourthfluid port 2504.

In one example of a parallel configuration, all fluid ports on a firstside of the stack except a bottom fluid port may be fitted with opennipples 2801. The bottom fluid port on the first side may be fitted witha closed nipple 2802. All fluid ports on a second side of the stackexcept the top fluid port may be fitted with open nipples 2801. The topfluid port on the second side may be fitted with a closed nipple.

FIG. 21B is a cross-sectional view of a membrane element 2400 stacked inseries, according to some embodiments. A top plate first fluid port 2501may direct a first fluid to a first fluid port 2401 of the head plate ofa first membrane element 2400. The first fluid may then pass through thefirst membrane element 2400. The first fluid may then pass to a secondmembrane element 2400 by exiting the first membrane element 2400 througha second fluid port 2402 located on the foot plate of the first membraneelement 2400. The second fluid port 2402 may be coupled to first fluidport 2401 of a second membrane element 2400 positioned beneath the firstmembrane element 2400. Similarly, the first fluid may pass through athird membrane element 2400. For a series configuration, the first fluidports 2402 and second fluid ports 2402 of each membrane element 2400 mayalternate between a first side and a second side of the membrane element2400. After passimg through the membrane element 2400, the first fluidmay directly exit the last membrane element 2400 through its secondfluid port 2402, or may pass through a bottom plate. Alternately, thefirst fluid may be routed back to the top plate and may flow out throughthe top plate second fluid port 2502.

A top plate third fluid port 2503 may direct a second fluid to a thirdfluid port 2403 of the head plate of a first membrane element 2400. Thesecond fluid may then pass through the first membrane element 2400. Thesecond fluid may then pass to a second membrane element 2400 by exitingthe first membrane element 2400 through a fourth fluid port 2404 locatedon the foot plate of the first membrane element 2400. The fourth fluidport 2404 may be coupled to the third fluid port 2403 of a secondmembrane element 2400 positioned beneath the first membrane element2400. Similarly, the first fluid may pass through a third membraneelement 2400. For a series configuration, the third fluid ports 2403 andfourth fluid ports 2404 of each membrane element 2400 may alternatebetween a first side and a second side of the membrane element 2400.After passing through the membrane element 2400, the second fluid maydirectly exit the last membrane element 2400 through its fourth fluidport 2404, or may pass through a bottom plate. Alternately, the secondfluid may be routed back to the top plate and may flow out through thetop plate fourth fluid port 2504.

In one example of a series configuration, the fluid ports on a firstside of the stack may alternate between being fitted with open nipples2801 and closed nipples 2802. Similarly, the fluid ports on a secondside of the stack may alternate between being fitted with open nipples2801 and closed nipples 2802, in which the first and second side mayhave alternating types of nipples. For example, whenever a fluid port onthe first side is fitted with an open nipple 2801, the correspondingfluid port on the second side may be fitted with a closed nipple 2802.

FIG. 23 is an isometric view of a membrane element 2400, according tosome embodiments. In some examples, a partially enclosed membraneelement 2400 may be immersed in a first fluid. In this configuration,the one or more openings associated with a first fluid may be exposed,thereby allowing the first fluid to enter and exit the membrane element2400. The membrane element 2400 may include a first fluid port 2401 anda second fluid port 2402 to plumb a second fluid through the membraneelement 2400. In some examples, the first fluid may be a feed fluid andthe second fluid may be a draw fluid. The membrane element 2400 may beimmersed in the feed fluid, allowing the feed fluid to pass through themembrane element 2400. The draw fluid may be plumbed through themembrane element 2400 as described above. Alternatively, the membraneelement 2400 may be immersed in the draw fluid while the feed fluid maybe plumbed into the membrane element 2400 by fluid ports, as describedabove. It may be advantageous to use this configuration for membranebioreactors.

FIG. 24 is an isometric view of a skid of membrane elements 2400,according to some embodiments. In some examples, many membrane elements2400 may be coupled in arrays that may be suitable for operation in alarge plant. Arrays may be formed by stacking membrane elements 2400together, and creating a fluid interface between the membrane elements2400 the array. The fluid interface may be in series, parallel, orcombinations thereof. One or more stacks may be combined in a commonframe 2701 to provide rigid endplates and mechanical support. A topfluid interface 2702 and a bottom fluid interface 2703 may provide afluid interface between different stacks, thereby providing a fluidinterface for the entire array. In addition, skids including multiplearrays may be provided. The skid may be a standalone module, and mayprovide pumps for one or more fluids and controls to run efficiently.Additionally, leak detection may be included at the skid level. The skidmay have headers that may couple each array in parallel. Modules may beisolated and removed from the skid for maintenance. In some examples,many skids may be used to operate a large plant.

Examples of membranes, elements, modules, and/or stacks described hereinmay generally be used to perform forward osmosis. Forward osmosisgenerally refers to a process whereby a solute in a draw solution isgreater than a solute in a feed solution. Water traverses the forwardosmosis membrane, generally from the feed to the draw solution,decreasing the concentration of solute in the draw. Any number ofsolutes may be manipulated using membranes, devices, and systemsdescribed herein including, but not limited to salts. Any number offluids may be used to implement the feed and draw fluids, including, butnot limited to, water, industrial waste, commercial waste, agriculturalwaste, and beverages. Pressure retarded osmosis generally refers to aprocess whereby energy or pressure is generated by fluid transportdriven by the osmotic pressure difference between a feed solution and adraw solution. The feed solution may be wastewater or river water andthe draw solution may be seawater or reverse osmosis brine. Membranedistillation generally refers to a process whereby fluid from a liquidfeed solution at a high temperature passes through a membrane as vaporand condenses to a permeate solution at a lower temperature. The feedmay be waste water, seawater, or any solution of high saltconcentration.

Example Performance

Example performance metrics achieved using examples of membrane plateassemblies described herein are provided below. The example metrics areprovided by way of example and to facilitate an understanding of exampleperformance achievable using assemblies described herein. The examplesprovided are not the only performance metrics achievable, and not allembodiments may achieve xe described performance.

TABLE 1 Performance of Porifera's Gen 1 membrane plate assembly.Membrane area per element 7.0 m2 Membrane Type Forward osmosisOperational pH limits 2-11 Water processed by element with 190-240 L/h5.5 wt % NaCl draw vs. water (FO mode) Reverse salt flux of element0.2-0.6 g/L Water processed by element with 65-75 L/h 5.5 wt % NaCl drawvs. 3.25% NaCl (FO mode) Feed spacer 0.030″ Fishnet Head loss 0.03psi/gpm Element volume, including housing 0.03 m3 Physical dimensions16″ × 18″ × 7″ Weight (wet) 72 lbs Materials Plastic & Aluminum PlumbingInterface Porifera Quick Change Manifold

TABLE 2 Performance of Porifera's Gen 1 membrane plate assembly in FOmode with different flow rates using 300 TDS Feed and 1M NaCl Draw. DrawFlow Feed Flow Flux Draw Head Feed Head rates rates at 25 C. RSF LossLoss (gpm) (gpm) (LMH) (g/L) (psi) (psi) 2.0 2.0 21.9 0.46 0 0.9 4.0 4.025.3 0.39 0 1.2 6.0 6.0 26.7 0.39 0.3 1.5 8.0 8.0 27.3 0.31 0.7 2.1 10.010.0 28.0 0.35 1.2 2.1

TABLE 3 Packing Density of Porifera's Elements compared to commercial ROand FO elements. Area Packing Density Element (m²) (m²/m³) RO 4040 7 m²7 263.7 RO 8040 - 41 m² 41 569.2 Porifera's Gen 2 - 80 80 615.0 m²Porifera's Gen 1 - 7 7 233.0 m² Commercial FO 8040 - 17 236.0 17 m²Commercial FO 4040 - 3 113.0 3 m² Commercial FO 4040 - 1.20 45.2 1.2 m²

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention.

What is claimed is:
 1. A spacer plate for a filtration membraneassembly, the spacer plate comprising: a rigid body defining: a firstsurface on a first side of the rigid body; a second surface on a secondside of the rigid body; a peripheral surface extending between the firstsurface and the second surface; a spacing region within the peripheralsurface; at least a first opening connected to the spacing region, atleast a second opening connected to the spacing region, a first membranebonding area on the first surface, the first membrane bonding area beingdefined by one or more projections or depressions on the first surface;and a second membrane bonding area on the second surface, the secondmembrane bonding area being defined by one or more projections ordepressions on the second surface, the second membrane bonding areabeing laterally offset from the first membrane bonding area.
 2. Thespacer plate of claim 1, further comprising a first membrane bonded tothe first surface at the first bonding area and a second membrane bondedto the second surface at the second bonding area.
 3. The spacer plate ofclaim 2, wherein the first opening is in fluid communication with aregion between the first and second membranes and at least partiallydefines a first flow path.
 4. The spacer plate of claim 3, wherein thesecond opening is in fluid communication with a region outside of thefirst and second membranes.
 5. The spacer plate of claim 1, furthercomprising a separating sheet extending across the spacing region and atleast partially defining the first surface and the second surface. 6.The spacer plate of claim 5, wherein the separating sheet includes oneor more protrusions, cavities, textures, or combinations of any of theforegoing, extending therefrom or therein.